The Eocrinoidea

Eocrinoids are among the earliest groups of
echinoderms to appear, ranging
from the Early Cambrian to the
Silurian. This one, Gogia,
is from the Middle Cambrian House Range
of Utah. Despite the name ("dawn crinoids"),
they are not directly ancestral to the true crinoids. Instead, various
echinoderms in the Blastoidea appear to have evolved from eocrinoid
ancestors; thus the Eocrinoidea is a
paraphyletic or polyphyletic
group.

Most eocrinoids were sessile and fed with their long brachioles
(the arm-like structures, which in this specimen are spirally twisted).
The body was covered by plates; in early eocrinoids the holdfast was also
covered by plates, but later eocrinoids evolved a stalk with columnals,
like crinoids and blastoids.